When the amount of pot that you have left fills the corner of your baggie, usually about a days worth is left. Its consistency resembles a dry powder, not the soft, stinky nuggets they once were.
I need to call Mr. Nice Guy and get somechronic before I run out. I got a serious case of the Cornerbag Blues.
The Mexican cartels sometimes use a cornerback (US born citizen)to traffic narcotics into America. Corners or cornerbacks are useful dealers because they live in the USA.